I just bought a used one in Jan. A friend's used equipment book listed low end at $4500, Average at $5800, and Good at around $6500. These may be off a couple hundred, but they're in the ballpark.
I would imagine that a new FEL would go for about $2000 or so and a decent belly mower no less than $500-750.
After owning a 180D for a couple of months, my opinion is that you go a good deal!!!